Trimmer potentiometer



Jan. 31, 1967 M. c. LAYLAND 3,302,155

TRIMMER POTENTIOMETER Original Filed Nov. 5, 1962 2 Sheets-Sheet l JmL3.1, 1967 M. c. L AYLAND 3,302,155

TRIMMER POTENTIOMETER original Filed Nov. 5, 1962 2 sheets-sheer 24757,12 INVENTOR.

United States Patent O 3,302,155 TRIMMER IGTENTIOMETER Michael C.Layland, Diamond Bar, Caiif., assigner to Dale Electronics, Inc.,Columbus, Nebr., a corporation of Nebraska Original application Nov. 5,1962, Ser. No. 235,575, now

Patent No. 3,233,201, dated Feb. 1, 1966. Divided and this applicationJan. 25, 1966, Ser. No. 522,952

7 Claims. (El. 3.38-183) This application is a divisional application ofmy copending application Serial Number 235,575 led November 5, 1962, nowissued into United States Patent No. 3,233,201 dated February l, 1966.

The mass production of miniature trimmer potentiometers has invited ahost of problems in fabrication and assembly of parts therefor. Myinvention relates to a trimmer potentiometer that is easily adaptable tomass production, and one that is capable of achieving maximumperformance standards.

A principal object of my invention is to provide a trimmer potentiometerwhich has an easily fabricated wiper arm assembly that will provideconstant uniform contact with the related components without causing anydamage thereto.

A further object of my invention is to provide a trimmer potentiometerwherein the wiper arm assembly provides clearance whereby maximum travelof the assembly can be achieved.

A still further object of my invention is to provide a trimmerpotentiometer wherein the wiper arms are easily secured to the wiperblock.

A still further object of my invention is to provide a trimmerpotentiometer wherein the wiper arm for the collector bar and the wiperarm for the resistance coil are comprised of a single piece of material.

A still further object of this invention is to provide a trimmerpotentiometer wherein the standard components thereof are mounted in onepart of the housing and the components which normally vary in design areseparately constructed in a second part of the housing so that the twohousings and components therefor can be mass produced separately andthen later combined to Acreate a plurality of potentiometers of varyingdesign capabilities.

A still further object of my invention is to provide a trimmerpotentiometer that can be easily detachably assembled for testing beforebecoming permanently assembled.

A still further object of this invention is to provide a trimmerpotentiometer wherein the resistance coil is selfaligned regardless ofthe amount of `windings thereon.

A still further object of my invention is to provide a trimmerpotentiometer that is easily sealed and which is self-sealing in atleast some respects.

A still further object of my invention is to provide a trimmerpotentiometer wherein the leadscrew is completely journaled in oneportion of the casing to prevent the sealing of the Icomposite parts ofthe casing at points adjacent the leadscrew.

A still further object of my invention is to provide a trimmerpotentiometer wherein the leadscrew is mounted in a self lubricatingbearing.

A still further object of my invention is to provide a trimmerpotentiometer that is economical in manufacture, durable in use, andrened in appearance.

These and other objects will be apparent to those skilled in the art.

My invention consists in the construction, arrangements, andcombination, of the various parts of the device, whereby the objects-contemplated are attained as hereinafter more fully set forth,specifically pointed out in my claims, and illustrated in theaccompanying drawings, in which:

FIGURE 1 is a side elevational view of my assembled 3,392,155 PatentedJan. 31, 1967 lCC device with a portion of the casing cut away to morefully illustrate its construction;

FIGURE 2 is a sectional view taken on line 2-2 of FIGURE 1;

FIGURE 3 is a top plan view of the lower case assembly;

FIGURE 4 is one end elevational view of the lower case assembly ofFIGURE 3;

FIGURE 5 is a side elevational view of the lower case assembly shown inFIGURE 3 with a portion of the -casing cut away to more fully show theconstruction thereof;

FIGURE 6 is a side elevational view of the top case assembly with aportion of the case cut away to more fully illustrate its construction;

FIGURE 7 is a bottom plan view of the wiper arm assembly;

FIGURE 8 is an end view of the wiper arm assembly shown in FIGURE 7;

FIGURE 9 is a schematic perspective view of the wiper arm assemblyshowing how the wiper arms are assembled on the wiper block;

FIGURE 10 is a perspective View of a spring clip element used in sealingthe assembled unit and to maintain the leadscrew against longitudinaldisplacement;

FIGURE 11 is an enlarged side elevational view of my assembled devicesimilar to that of FIGURE 1 showing the screw assembly and related partsthrough a cut out portion of the upper and lower cases;

FIGURE 12 is a sectional view of my assembled device taken on line 12-12of FIGURE 11;

FIGURE 13 is an enlarged sectional view of one end of the screwassembly;

FIGURE 14 is a perspective View of a different form of clip element;

FIGURE 15 is a partial sectional view of my device similar to that ofFIGURE 13 but showing the use of the clip in FIGURE 14;

FIGURE 16 is a sectional view similar to that of FIG- URE 12, but takenthrough a modified form of my invention; and

FIGURE 17 is a sectional view similar to that of FIG- URES 12 and`l6,but taken through a second modified form of my invention.

I have used the numeral 10 to generally designate a housing comprised ofa top case or casing 12 and a lower case or casing 14. The lower casing14 is comprised of a normally horizontally disposed rectangular casingof plastic or the like with a at bottom and side walls that taperupwardly and outwardly so that the top width thereof is greater than thewidth at the bottom thereof. The bottom and sides of lower casing 14 areclearly shown in FIGURES 2 and 12. An elongated depression 16 appears inthe top and to one side of casing 14 and extends substantially the fulllength of the casing. As shown in FIGURE 12, depression 16 has verticalside walls which terminate in a V-shaped bottom portion. An elongatedshoulder 18 protrudes from the top of lower lcasing 14 and extends inparallel fashion to depression 16. An inverted L-shaped collector bar26, which is of electro-conducting material, is rigidly mounted onshoulder 18 in any convenient manner such as by a suitable adhesive. Anelongated cylindrical core 22 with a plurality of windings 24 on itsouter surface is held in depression 16 by a suitable adhesive, as shownin FIG- URE 12. The V-shaped bottom of depression 16 permits theresistance coil 26, comprised of core 22 and windings 24, to beprecisely aligned within casing 14 regardless of variations in thediameter thereof. The elevations of the tops of collector bar 26 andresistance coil 26 are substantially the same, as shown in FIGURE 12.Termination tabs 28 and 30 are secured to the opposite o el ends ofresistance coil 26. A U-shaped raceway 38 is formed in one end'of lowercasing 14 as indicated in FIGURES 3 and 4, and fiexible electrical leads32, 34 and 36 extend into the casing from the exterior thereof. Lead 32is secured to tab 28; lead 34 extends between the resistance coil 26 andcollector bar 20 to be secured to tab 30, and lead 36 is secured to oneend of the collector bar. Both ends of casing 14 terminate in a shelf 48of reduced thickness.

The top or upper casing 12 is rectangular in shape and has a compartment42 which is partially complementary in shape to lower casing 14 so thatthe casing can be received within the compartment. A shoulder 44 appearsalong the vertical side walls of compartment 42 to engage the top oflower casing 14 to limit the penetration of the lower casing into thecompartment. Shoulders 45 at the ends of casing 12 engage the shelves 40on the ends of casing 14 to accomplish this same purpose. The bottoms ofboth the upper and lower casings thereupon appear in the same horizontalplane. Wedge-shaped openings 46 appear between the tapered sides ofcasing 14 and the vertical interior walls of compartment 42 and theseopenings are filled with a suitable adhesive when it is desired topermanently secure and seal the two -casings 12 and 14 i together. Asshown in FIGURE 11, the portion of casing 12 adjacent the ends of casing14 is tapered to present a wedge-shaped opening 47 into which a suitableadhesive can also be placed.

A horizontal bore 48 extends into one end of upper casing 12 and has atapered portion 58 which terminates in horizontal bore 51, which, inturn communicates with the upper portion of compartment 42. A bore t) isin axial alignment with bores 48 and 51 and is located in the other endof casing 12. A screw 54 extends through these bores and includes a headand shank 56 and 5S which are rotatably positioned in bores 48 and 50,respectively, and are complementary in shape to these bores. A resilientsealing ring 69 is mounted between the tapered portion of bore 48 andthe corresponding tapered portion of head 56. The diameter of screw 54decreases as it extends from the end of casing 12 into compartment 42. Ashoulder 62 is formed on screw 54 in spaced relation to the end 64 ofcompartment 42, as shown in FIGURE 13. The inward side of shoulder 62appears closely adjacent an arcuate protrusion 65 which extendsdownwardly over screw 54 from the top of compartment 42. This structureis shown in FIGURES ll and 12. A resilient arcuate-shaped clip 66 with ascrew receiving slot 68 has its vertical side edges in engagement withthe end 64 of compartment 42. Clip 66 is forcibly positioned between theshoulder 62 on screw 54 and the end of the compartment as the screw isreceived in slot 68 of the clip. The confined space between the shoulder62 and the end 64 ofthe compartment 42 causes clip 66 to be at leastpartially flattened when positioned in this space. The tendency of theclip to resume its normal arcuate position exerts an inward longitudinalforce on the screw. This force causes sealing ring 60 to compress tohelp seal compartment 42. Also, this action not only prevents theinadvertent removal of the screw from the casing 12, but it also holdsthe screw against longitudinal play The remainder of screw is comprisedof threaded portion 68 except for the extreme outer end thereof which isrotatably journaled in bore S0.

In FIGURES 14 and l5, I have shown an alternate form of clip 66A whichmay be of any desired shape, but which should have a slot 68A therein toreceive screw 54. Clip 66A is generally flat but serves as a wedgebetween shoulder 62 and the end 64 of compartment 42 to compress sealingring 60 in the same manner that clip 66 accomplished this result,namely, by exerting inwardly longitudinal pressure on the screw 54. Bothof the clips 66 and 66A can be of a material having self-lubricatingproperties. Such a material is Otilite, but any such substance of powdermetallurgy or the like will serve equally well.

A wiper block 78 has a threaded horizontal bore 72 which is adapted forthreadable rotation on threaded portion 68 of screw 54. Wiper block 70is generally rectangular in shape and is slidably mounted between thevertical walls at the top of compartment 42. An elongated recess 74appears in the bottom of wiper block 70, which is comprised of plasticor the like, and recesses 76 and 78 extend at right angles thereto onopposite sides thereof. Recesses 76 and 78 are parallel but are not inalignment. A wiper assembly 80 of electro-conducting materialiscomprised of a single piece of material, and includes an elongated strip82 with wiper arms 84 and 86 extending transversely therefrom onopposite sides thereof. Each arm is folded back upon itself andterminates in an arcuate contact surface area 88. Portions of wiperassembly 80 are complementary to the recesses in wiper block 70 and arereceived therein. The wiper block can lbe heat-treated so that beads orthe like will form to bind the wiper assembly to the block. As shown inFIG- URES 2 and 11, the arcuate contact surface areas 88 on arms 84 and86 are in resilient sliding engagement with collector bar 28 andresistance coil 26, respectively. The protrusion 65 near one end ofscrew 54 limits the longitudinal displacement of wiper block 7 0.

In FIGURE 16 I have shown a modied form of my device which is similar tothe above described structure except for the collector bar structure andassembly. The original shoulder 18 is replaced by a shoulder 18A whichhas an elongated V-shaped groove 16A therein similar in cross sectionand parallel to the depression or groove 16 which houses the resistancecoil 26. Original collector bar 28 is replaced by hollow cylindrical ortubular collector bar 20A which is held in groove 16A by a suitableadhesive. In this form of my invention, lead 34 is permitted to passthrough the center of the collector bar 28A. This structure serves toconserve space, and the parallel grooves 16A and 16 insure that thecollector bar 28A and resistance coil 26 will always be aligned.

The form of the invention shown in FIGURE 17 is similar to that ofFIGURE 16 but the collector bar 28B thereof is a solid cylindrical rod.The cylindrical shape of collector bars 28A and 26B provide a betterContact surface and is less likely to become coated with dirt or debris.Furthermore, ease of fabrication of the bars and assembly in the grooves16A is achieved by this cylindrical construction.

The normal operation of my device is as follows: The resistance impartedto the elecrtical circuitry associated with my trimmer potentiometer isdetermined in the conventional manner by rotating the screw 54 to alterthe position of the wiper block 70 and the wiper arm 86 with respect tothe resistance coil 26. My unit permits the assembly of the screw 54 andthe related wiper block 78 and wiper assembly 88 to be assembled inlarge quantities independently of the rest of the potentiometer. Thesealing and connecting characteristics of the clips 66 and 66A in regardto screw 54 and the upper casing 12 have already been discussed, but itshould be noted that since no seam in housing 10 occurs along thelongitudinal axis of screw 54, the difficult task of creating such aseal is avoided,

The resistance coil 26 can be wound to any desired specification andplaced in the V-shaped bottom portion of depression 16 and can berigidly secured therein by a suitable adhesive. The tapered walls of thebottom of depression engage and align the resistance coil regardless ofits diameter.,

The assembled lower casing 14 can then be positioned in the assembledupper casing 12 as shown in FIGURE l2. The two casings can betemporarily held together by any convenient external means, and thepotentiometer can then be tested to insure the operability thereof. Ifany malfunctions are noted during testing, the two casings, not yethaving been permanently united, and then be separated and repaired, orif one assembly is totally defective, the other assembly can normally besalvaged and matched with a substituted easing.

Substantial production costs are saved by creating the wiper assembly 80from a single piece of metal which provides both the wiper arm 84 forthe collector bar 20 and the wiper arm 86 for the resistance coil 26.These fabrication costs are further reduced by the means of securing thewiper assembly 80 to the wiper block 70. The recesses 74, 76 and 78stabilize the wiper assembly 80 and lthe subsequently formed beads 90lock the assembly to the block. Beneficial spring action is affordedeach of the wiper arms 84 and 86 by bending them substantially 180degrees from each side of the wiper block 70, and permitting them toextend back substantially to the opposite side of the wiper block. Thisspring action which is built into each of the wiper arms helps to insurea constant positive contact with the collector bar 20' (or collectorbars 20A or 20B) and the resistance coil 26. The arcuate contactsurfaces 88 on each of the arms 84 and 86 provide an adequate surfacewhile at the same time, wear on the resistance coil and collector bar isminimized. The accumulation of debris by the collector arms is alsominimized by these arcuate contact surfaces, particularly when used onthe collector bars 20A or 20B. Since both of the arms 84 and 86 extendlaterally from block 70, they do not shorten or limit the longitudinaldisplacement of the block on screw 54.

After the potentiometer has been assembled and successfully tested, asuitable adhesive is then placed in the wedge-shaped openings thatseparate the two casings 12 and 14. A suitable adhesive or sealingsubstance (not shown) is placed around leads 32, 34 and 36 in raceway38, and with sealing ring 60 sealing the tapered portion of bore 48, thehousing is effectively sealed.

Thus, from the foregoing, it is seen that my device will accomplish atleast all of its stated objectives.

Some changes may be made in construction and arrangement of my trimmerpotentiometer without departing from the real spirit and purpose of myinvention, and it is my intention to cover by my claims, any modifiedforms of structure or use of mechanical equivalents which may bereasonably included within their scope.

I claim:

1. In a potentiometer,

a housing,

a bearing means in said housing,

a leadscrew of integral solid construction rotatably secured in saidbearing means, said lea-dscrew having at least limited longitudinalmovement in said bearing means,

a resistance coil secured in said housing,

a collector bar secured in said housing,

wiper contact means movably mounted on said leadscrew and in engagementwith said collector bar and said resistance coil,

a bore in said housing and communicating with the exterior thereof,

one end of said leadscrew extending into said bore,

at least a portion of said leadscrew yand said bore having closelyadjacent opposing surfaces diagonally disposed with respect to thelongitudinal axis of said bore,

the diagonally disposed opposing surface of said leadscrew comprising aIportion of its length wherein its diameter is progressively decreasedfrom a head portion of larger diameter to a center portion of reduceddiameter,

a resilient sealing means intermediate the adjacent opposing surfaces ofsaid leadscrew and said bore,

retaining means on said leadscrew urging said leadscrew in one directionof longitudinal movement to move the opposing surfaces of said leadscrewand said bore together to compress said sealing means,

and electrical connecting means on said collector bar and saidresistance coil for connecting said poten-` tiometer in an electricalcircuit.

2. The structure of claim l wherein said sealing means is a ring ofresilient material.

3. The structure of claim 1 wherein the retaining means on saidleadscrew includes a shoulder rigidly secured to said leadscrew andloosely positioned between two spaced apart projections on said housing,and a clip on said leadscrew forcibly urging said shoulder into abuttingrelation with one of said projections on said housing.

4. The structure of claim 3 wherein said clip is comprised of aresilient material.

5. The structure of claim 3 wherein said clip is resilient and arcuatein shape and is partially compressed towards a flattened conditionbetween said shoulder and one of said projections.

6. The structure of claim 3 wherein said clip is substantially flat andis forcibly wedged between said shoulder and one of said projections.

7. In a potentiometer,

a housing having a leadscrew rotatably secured in said housing,

a resistance coil secured in said housing,

a collector bar secured in said housing,

wiper contact means movably mounted on said leadscrew and in engagementwith said collector bar and said resistance coil,

a bore in said housing and communicating with the exterior thereof,

one end of said leadscrew extending into said bore,

at least a portion of said leadscrew and said bore having closelyadjacent opposing surfaces diagonally disposed with respect to thelongitudinal axis of said bore and said leadscrew,

the diagonally disposed opposing surface of said leadscrew comprising aportion of its length wherein its diameter is progressively decreasedfrom a head portion of larger diameter to a center portion of reduceddiameter,

a resilient sealing means intermediate the adjacent opposing surfaces ofsaid leadscrew and said bore,

a shoulder means rigidly secured to said leadscrew and being positionedin said housing adjacent the portion of said housing adjacent the innerend of said bore,

a resilient arcuate clip on said leadscrew and in engagement with saidshoulder and the portion of said housing adjacent the inner end of saidbore wherein said clip `is partially compressed towards a attenedcondition between said shoulder and the portion of said housing adjacentthe inner end of said bore; and said resilient sealing means ispartially compressed between the diagonally disposed surfaces in saidbore and on said leadscrew to effect a tight seal of said housing evenwhen said sealing means becomes worn through repeated rotation of saidleadscrew;

said clip maintaining a constant compression on said sealing means andmoving said leadscrew and the opposing surface thereon towards theopposing surface of said bore to continue to compress said sealing meanseven when said sealing means becomes worn through repeated rotation ofsaid leadscrew,

an electrical connecting means on said collector bar and said resistancecoil for connecting sa-id potentiometer in an electrical circuit.

References Cited by the Examiner UNITED STATES PATENTS 472,288 4/ 1892Edison 277-115 X 2,895,116 7/1959 Morrison 338-180 2,934,733 4/1960Green et al. 338-148 2,958,062 l0/l960 Barden et al. 338-180 2,976,5073/ 1961 Di Girolamoa et al. 338-180 3,050,704 8/1962 Dickinson et al.338-180 ANTHONY BARTIS, Primary Examiner.

1. IN A POTENTIOMETER, A HOUSING, A BEARING MEANS IN SAID HOUSING, ALEADSCREW OF INTEGRAL SOLID CONSTRUCTION ROTATABLY SECURED IN SAIDBEARING MEANS, SAID LEADSCREW HAVING AT LEAST LIMITED LONGITUDINALMOVEMENT IN SAID BEARING MEANS, A RESISTANCE COIL SECURED IN SAIDHOUSING, A COLLECTOR BAR SECURED IN SAID HOUSING, WIPER CONTACT MEANSMOVABLY MOUNTED ON SAID LEADSCREW AND IN ENGAGEMENT WITH SAID COLLECTORBAR AND SAID RESISTANCE COIL, A BORE IN SAID HOUSING AND COMMUNICATINGWITH THE EXTERIOR THEREOF, ONE END OF SAID LEADSCREW EXTENDING INTO SAIDBORE, AT LEAST A PORTION OF SAID LEADSCREW AND SAID BORE HAVING CLOSELYADJACENT OPPOSING SURFACES DIAGONALLY DISPOSED WITH RESPECT TO THELONGITUDINAL AXIS OF SAID BORE, THE DIAGONALLY DISPOSED OPPOSING SURFACEOF SAID LEADSCREW COMPRISING A PORTION OF ITS LENGTH WHEREIN ITSDIAMETER IS PROGRESSIVELY DECREASED FROM A HEAD PORTION OF LARGERDIAMETER TO A CENTER PORTION OF REDUCED DIAMETER, A RESILIENT SEALINGMEANS INTERMEDIATE THE ADJACENT OPPOSING SURFACES OF SAID LEADSCREW ANDSAID BORE, RETAINING MEANS ON SAID LEADSCREW URGING SAID LEADSCREW INONE DIRECTION OF LONGITUDINAL MOVEMENT TO MOVE THE OPPOSING SURFACES OFSAID LEADSCREW AND SAID BORE TOGETHER TO COMPRESS SAID SEALING MEANS,AND ELECTRICAL CONNECTING MEANS ON SAID COLLECTOR BAR AND SAIDRESISTANCE COIL FOR CONNECTING SAID POTENTIOMETER IN AN ELECTRICALCIRCUIT.